There is a need, in the field of biomaterial implantation, for resorbable and swellable particles. However, only incomplete solutions have been devised thus far.
Thus, gelatin sponges are biodegradable after implantation in tissues or injection in cavities, ducts or vessels. They can be impregnated with physiological saline and/or contrast media.
However, after their hydration they loose their shape and resistance. In addition, there is a great variability in resorption speed, which is influenced by many factors such as nature, homogeneity, size, enzymatic potential, and local inflammatory response. Moreover, since the mass of resorbable gelatin may vary in large proportions, the resorbtion time of the plug will consequently also take a variable time.
Another attempt consists of dextran starch microspheres (Spherex® from Pharmacia; Embocept® from Pharmacept) which have been devised to provide for resorbable implants. Indeed these dextran starch microspheres, which are non-toxic, are readily degradable and are notably used to provide temporary vascular occlusion, mainly for the treatment of tumor when co-administered with chemotherapeutic drugs.
However, dextran starch microspheres suffer from several limitations. First of all, these microsphers are available only in small sizes, with diameters below 100 μm. Such a small diameter does not allow targeted embolization, particularly for proximal occlusion. Besides, resorption is fast, with a usual half life below 1 hour, and cannot be accurately predicted since depends on the enzymatic capability to resorb a given microspheres volume.
Water-absorbent dry microspheres based on acrylic and PVA copolymers have also been proposed as swellable implants (Osuga et al. (2002) J Vasc Intery Radiol. 13:929-34). In a commercial presentation (Quadrasphere®, Biosphere Medical), these microspheres are under a dry form. For their use they are mixed with physiological saline, and/or iodinated contrast media. Compared to their initial size, their final size after water uptake varies according to the ionic charge of the medium (×2 or ×4 in saline and contrast medium respectively).
However the final size varies too much to allow for their controlled final volume after implantation, which is a serious limitation for their use. Besides, these microspheres are not resorbable.
It is therefore a goal of the present invention to solve the above problems.